The present disclosure relates to a drive circuit allowing an extra space for a timing margin, and a display unit and an electronic apparatus each provided with the drive circuit.
In a field of display units performing picture display, a display unit using, as a light emitting element of a pixel, a current drive type optical element whose light emission luminance is varied in response to a value of a flowing current, for example, an organic electro luminescence (EL) element, has been developed and commercialization thereof is progressing. Unlike a liquid crystal element, the organic EL element is a self light emitting element. Therefore, since a light source (a backlight) is unnecessary in the display unit using the organic EL element (an organic EL display unit), the display unit is allowed to be reduced in weight, in thickness, and improved in luminance, as compared with a liquid crystal display unit demanding a light source. Further, since a response speed of the organic EL element is about several μs, which is extremely high, an after image during moving picture display does not occur. Accordingly, the organic EL display unit is expected to be a mainstream of next generation flat panel display.
In the organic EL display unit, the drive method thereof includes a simple (passive) matrix method and an active matrix method, as with the liquid crystal display unit. The former has a simple configuration; however, has a difficulty to achieve a large display unit with high definition. Therefore, development of the active matrix method has been actively carried out. In this method, a current flowing through an organic EL element arranged for each pixel is controlled by a drive transistor in a pixel circuit that is provided for each organic EL element.
In the active matrix organic EL display unit, the scan lines are sequentially scanned and a signal voltage based on a picture signal is sampled and written to a retention capacitance, in every horizontal period (1H). In other words, writing operation of the signal voltage is performed by linear sequential scanning of 1H period. Moreover, in the organic EL display unit, when a threshold voltage and a mobility of the drive transistor are varied for each pixel, light emission luminance of organic EL element is varied and uniformity of a screen is impaired. Therefore, in the active matrix organic EL display unit, correction operation to reduce variation of light emission luminance caused by variation of the threshold voltage and the mobility of the drive transistor is performed together with the linear sequential scanning of 1H period.
In the active matrix organic EL display unit, a large current is allowed to flow through power lines because power is supplied to the pixels through the respective power lines. However, a pulse power controlling light emission and light extinction of the organic EL element is normally applied to the power lines. Therefore, the scale of the power line drive circuit becomes extremely large, and the bezel of the display panel including the power line drive circuit therein becomes large as well. Therefore, for example, as described in Japanese Unexamined Patent Application Publication No. 2012-137513, it is proposed that the voltage of the power lines is fixed, and the data pulse applied to the signal lines is formed of a waveform having three values in 1H.